Construction of Ultrathin Cobalt-Based Nanosheet Arrays on Titanium Mesh as Asymmetric Electrodes for Overall Water Splitting

Abstract

Developing highly efficient and stable electrocatalysts is the key to realize hydrogen production from industrial electrolytic water. In this study, we constructed Co(OH) 2 and CoP ultrathin nanosheet arrays on titanium mesh using electrodeposition and phosphating processes. In alkaline conditions, the Co(OH) 2 /Ti-2.0 needed overpotentials of 414 and 457 mV to achieve 500 and 1000 mA cm −2 for oxygen evolution reaction. Mechanism research showed that CoOOH formed by preoxidation of Co(OH) 2 was the actual active substance. After low-temperature phosphorization of Co(OH) 2 , CoP nanosheets generated abundant defects and increased reactive sites, and CoP/ Ti-2.0 exhibited high activity in the all-pH hydrogen evolution reaction (overpotentials of 106, 116, and 131 mV in acidic, alkaline, and neutral solutions at 10 mA cm −2 , respectively). Density functional theory calculations showed the free energy of hydrogen adsorption of CoP. As efficient electrode materials, the Co(OH) 2 and CoP ultrathin nanosheet arrays on Ti mesh can be assembled to an alkaline electrolyzer, which required only 1.530 V to drive 50 mA cm −2 for overall water splitting with strong durability.

Saturn-like N-Doped VS2 Cathode with a Three-Step Deintercalation Mechanism under a Wide Voltage Range for Enhancing the Electrochemical Kinetics of Zinc-Ion Batteries

“…With the increasing market demand for lithium-ion batteries (LIBs), the contradiction between the shortage of lithium metal resources and uneven distribution becomes more and more prominent. − In addition, lithium metal has a low equilibrium electrode potential, and lithium dendrites will be generated in the cycle of LIBs, which may induce short circuit and cause combustion and explosion of organic electrolytes. − These two important defects seriously limit their large-scale application. Therefore, it is imperative to develop secondary batteries with a water system, low cost, and high energy density. − Aqueous-system zinc-ion batteries (ZIBs) are a kind of electrochemical energy storage system with a water-based electrolyte instead of an organic electrolyte, which have the advantages of better safety, greener, more relaxed manufacturing conditions, and higher ionic conductivity. − Metal zinc is rich in resources and has low price, stable chemical properties, and low redox potential (−0.76 V vs SHE). − Therefore, ZIBs have become a very ideal energy storage device.…”

Efficient Integrated Electrode Enables High-Current Operation and Excellent Stability for Green Hydrogen Production

“…In the present electrolysis markets, alkaline electrolysis is the earliest and most mature technique to produce “green hydrogen”. However, disadvantages of alkaline electrolysis, including low partial load range, limited current density, and low operating pressure, urge people to develop advanced electrolysis devices to ensure compatibility with fluctuated sustainable energy sources. − In the 1960s, General Electric first developed water electrolyzers based on solid polymer electrolytes. , The developed proton exchange membrane (PEM) has the advantages of high proton conductivity, low gas crossover, high-pressure operation, and compact system design. − Nowadays, PEM electrolyzer cells (PEMECs) have been considered as one of the most promising candidates for commercial sustainable hydrogen production. Advantages of the PEMEC include high current density (above 2 A/cm 2 ), high hydrogen pressure, high hydrogen purity, long durability, etc.…”